Refrigeration cycle device

ABSTRACT

To provide a refrigeration cycle device that has a refrigerant flow path with a structure to form a counter flow of air and refrigerant not only during cooling, but also during heating, and that allows low-pressure two-phase refrigerant to flow through a liquid pipe and can thereby reduce the amount of refrigerant needed. The refrigeration cycle device includes: an outdoor unit  1  including a compressor  5 , a four-way valve  6 , an outdoor heat exchanger  7 , and an outdoor expansion valve  9 , the four-way valve  6  being configured to switch between cooling operation and heating operation; an indoor unit  2  including an indoor heat exchanger  12  and an indoor expansion valve  14 ; and a gas pipe  3  and a liquid pipe  4  configured to connect the outdoor unit  1  and the indoor unit  2 ; and at least either one of a first bridge circuit  10  having a configuration including a plurality of flow path opening-closing units  11  to allow the refrigerant to flow through the outdoor heat exchanger  7  in the same direction both during the cooling operation and during the heating operation, and a second bridge circuit  15  having a configuration including a plurality of flow path opening-closing units  16  to allow the refrigerant to flow through the indoor heat exchanger  12  in the same direction both during the cooling operation and during the heating operation.

TECHNICAL FIELD

The present disclosure relates to a refrigeration cycle device thatconditions air, and particularly relates to a refrigeration cycle deviceconfigured to be capable of switching between cooling operation andheating operation.

BACKGROUND ART

Many of the current refrigeration cycle devices that condition air areconfigured to change the refrigerant flow directions to select eithercooling operation or heating operation.

In recent years, for the purpose of reducing the global warmingperformance (GWP) of refrigerant filled in a refrigeration cycle device,application of a non-azeotropic refrigerant mixture, in which multipletypes of refrigerants with different boiling points are mixed together,has been under consideration.

The non-azeotropic refrigerant mixture has properties that thesaturation temperature varies between the process of condensation andthe process of evaporation. In view of that, a heat exchanger thatexchanges heat between air and refrigerant is designed to have a flowdirection of air and a flow direction of refrigerant such that heat isexchanged between the air on its inlet side and the refrigerant on itsoutlet side, and such that heat is exchanged between the refrigerant onits inlet side and the air on its outlet side. That is, the heatexchanger is designed to form such a counter flow as to easily ensure asufficient temperature difference between air and refrigerant in theentirety of the heat exchanger.

However, in a refrigeration cycle device that switches between therefrigerant flow direction for cooling operation and the refrigerantflow direction for heating operation, when either the flow direction forcooling operation or the flow direction for heating operation isselected, the heat exchanger forms a parallel flow of refrigerant andair, which degrades its performance.

A method to avoid the problems as described above has been known asemploying a bridge circuit that uses a plurality of check valves tothereby prevent the positions of refrigerant inlet and refrigerantoutlet of a heat exchanger from being reversed between during coolingand during heating, so that the heat exchanger forms a counter flow ofrefrigerant and air not only during cooling, but also during heating(for example, Patent Literature 1).

CITATION LIST Patent Literature

Patent Literature 1: Japanese Unexamined Patent Application PublicationNo. H09-178283

SUMMARY OF INVENTION Technical Problem

However, in the refrigeration cycle device having the configuration asdisclosed in Patent Literature 1, condensed and liquified high-pressurerefrigerant flows through a liquid pipe extending between an outdoorheat exchanger and an indoor heat exchanger not only during coolingoperation, but also during heating operation. This results in a problemthat the amount of refrigerant needed is increased.

In addition, the indoor side expansion valve needs to be fully closedwhen cooling operation is selected, and the outdoor side expansion valveneeds to be fully closed when heating operation is selected. Thisresults in a problem that the expansion valves frequently operate to beopened and closed, which degrades the durability of the expansionvalves.

The present disclosure has been made to solve the above problems, and itis an object of the present disclosure to provide a refrigeration cycledevice that has a configuration in which at least either one of anoutdoor heat exchanger and an indoor heat exchanger forms a counter flownot only during cooling, but also during heating, and that can reducethe amount of refrigerant needed.

Solution to Problem

To achieve the above object, a refrigeration cycle device according toan embodiment of the present disclosure includes:

-   an outdoor unit including a compressor, a four-way valve, an outdoor    heat exchanger, and an outdoor expansion valve, the four-way valve    being configured to switch between cooling operation and heating    operation;-   an indoor unit including an indoor heat exchanger and an indoor    expansion valve; and-   a gas pipe and a liquid pipe configured to connect the outdoor unit    and the indoor unit to form a refrigerant circuit, the refrigerant    circuit being filled with a non-azeotropic refrigerant mixture,    wherein-   the refrigeration cycle device comprises at least either one of    -   a first bridge circuit accommodated in the outdoor unit, the        first bridge circuit having a configuration including a        plurality of flow path opening-closing units to allow the        non-azeotropic refrigerant mixture to flow through the outdoor        heat exchanger in a same direction both during the cooling        operation and during the heating operation, a flow path        opening-closing unit of the plurality of flow path        opening-closing units, installed in a flow path connecting the        liquid pipe and an outlet side of the outdoor heat exchanger,        being the outdoor expansion valve, and    -   a second bridge circuit having a configuration including a        plurality of flow path opening-closing units to allow the        non-azeotropic refrigerant mixture to flow through the indoor        heat exchanger in a same direction both during the cooling        operation and during the heating operation, a flow path        opening-closing unit of the plurality of flow path        opening-closing units, installed in a flow path connecting the        liquid pipe and an outlet side of the indoor heat exchanger,        being the indoor expansion valve. Advantageous Effects of        Invention

In the refrigeration cycle device according to an embodiment of thepresent disclosure, the first bridge circuit and the second bridgecircuit allow the outdoor heat exchanger and the indoor heat exchangerto form a counter flow both during cooling and during heating. Thus,even when a non-azeotropic refrigerant mixture is applied asrefrigerant, the heat exchangers still ensure a sufficient temperaturedifference between air and the refrigerant from their inlet to outlet,and can thereby exchange heat efficiently, so that the performance ofthe refrigeration cycle device is improved.

The refrigerant flowing through the liquid pipe is brought into alow-pressure two-phase state not only during cooling operation, but alsoduring heating operation. The liquid pipe is not filled with liquidrefrigerant in any operational state, so that the amount of refrigerantfilled in the refrigerant circuit can be reduced.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a refrigerant circuit configuration diagram of a refrigerationcycle device according to Embodiment 1.

FIG. 2 is a schematic diagram illustrating a relationship between an airflow direction and a refrigerant flow path of an outdoor heat exchangeraccording to Embodiment 1.

FIG. 3 is a graph illustrating an example of temperature variations fromwhen refrigerant and air enter a condenser to when the refrigerant andthe air flow out of the condenser.

FIG. 4 is a graph illustrating an example of temperature variations fromwhen refrigerant and air enter an evaporator to when the refrigerant andthe air flow out of the evaporator.

FIG. 5 is a refrigerant circuit configuration diagram of a refrigerationcycle device according to Embodiment 2.

FIG. 6 is a sectional view illustrating the configuration of the flowpath extending from an indoor heat exchanger outlet to a liquid pipe inan indoor bridge circuit according to Embodiment 2.

FIG. 7 is a refrigerant circuit configuration diagram of a refrigerationcycle device according to Embodiment 3.

FIG. 8 is a refrigerant circuit configuration diagram of a refrigerationcycle device according to Embodiment 4.

DESCRIPTION OF EMBODIMENTS

Hereinafter, the refrigeration cycle device according to the embodimentsof the present disclosure will be described in detail with reference tothe drawings. Note that the same or equivalent components in thedrawings below are denoted by the same reference numerals, anddescriptions thereof are not repeated.

Embodiment 1 Configuration of Refrigeration Cycle Device

FIG. 1 is a refrigerant circuit configuration diagram of a refrigerationcycle device according to Embodiment 1 of the present disclosure. Asillustrated in FIG. 1 , in a refrigeration cycle device 100, an outdoorunit 1 and an indoor unit 2 are connected by a gas pipe 3 and a liquidpipe 4, forming a single refrigerant circuit. This refrigerant circuitis filled with R407C that is a refrigerant mixture of three types of HFCrefrigerants with different boiling points. The refrigerant to be filledis not limited to this refrigerant mixture. For example, a refrigerantmixture of HFO refrigerants, R1234yf and R32, may also be employed. Arefrigerant mixture containing an HC refrigerant such as R290 or anatural refrigerant such as CO₂ as one of the components may also beemployed.

The outdoor unit 1 has a compressor 5, a four-way valve 6, an outdoorheat exchanger 7, an outdoor fan 8, and an outdoor bridge circuit 10incorporated therein. The operational capacity of the compressor 5 isadjustable. On the upstream side and the downstream side of the outdoorheat exchanger 7, an outdoor inlet header 17 a and an outdoor outletheader 17 b are installed that each have an end connected to the outdoorbridge circuit 10 on the opposite side to the outdoor heat exchanger 7.The outdoor fan 8 provided along with the outdoor heat exchanger 7changes the amount of air delivered to the outdoor heat exchanger 7 toadjust the amount of heat exchange between refrigerant and outside air.

The outdoor bridge circuit 10 includes four inlet/outlet ports in totalat one end of the outdoor inlet header 17 a described above, at one endof the outdoor outlet header 17 b described above, at one end of thefour-way valve 6, and at a connection end with the liquid pipe 4. Theoutdoor bridge circuit 10 is made up of three check valves 11 a, 11 b,and 11 c, and an outdoor expansion valve 9. The outdoor expansion valve9 has a configuration in which its valve body is movable by a pulsemotor or other motor. The opening degree of the outdoor expansion valve9 is adjustable continuously from a fully closed state to a fully openedstate. In the outdoor bridge circuit 10, a refrigerant flow path isformed such that refrigerant flows toward the indoor inlet header 17 anot only during cooling operation in which refrigerant enters from thefour-way valve 6, but also during heating operation in which refrigerantenters from the liquid pipe 4.

The indoor unit 2 has an indoor heat exchanger 12, an indoor fan 13, andan indoor bridge circuit 15 incorporated therein. The indoor fan 13 isconfigured to adjust the amount of heat exchange between refrigerantflowing through the indoor heat exchanger 12 and the room air. Atopposite ends of the indoor heat exchanger 12, an indoor inlet header 18a and an indoor outlet header 18 b are installed, while being connectedto the indoor bridge circuit 15 at an end of the respective headers onthe opposite side to the indoor heat exchanger 12.

The indoor bridge circuit 15 includes three check valves 16 a, 16 b, and16 c, and an indoor expansion valve 14. Similarly to the outdoorexpansion valve 9, the opening degree of the indoor expansion valve 14is adjustable continuously from a fully closed state to a fully openedstate. In the indoor bridge circuit 15, a refrigerant flow path isformed such that refrigerant flows through the indoor heat exchanger 12from the indoor inlet header 18 a not only during cooling operation inwhich refrigerant enters from the liquid pipe 4, but also during heatingoperation in which refrigerant enters from the gas pipe 3.

FIG. 2 is a schematic diagram illustrating a relationship between an airflow direction and a refrigerant flow path of the outdoor heat exchanger7. The outdoor heat exchanger 7 is made up of a plurality of heattransfer tubes 19 and a plurality of layered fins 20. The heat transfertubes 19 are circular tubes made of copper. In the present embodiment,the heat transfer tubes 19 are lined up in six in the vertical directionand arranged in four rows in the air flow direction. The fins 20, eachof which is a thin plate made of aluminum with a thickness ofapproximately 0.1 mm, are layered with a 1 to 2 mm spacing in between.

A flow of refrigerant into the outdoor heat exchanger 7 is divided atthe outdoor inlet header 17 a into three flows. The three flows ofrefrigerant enter the outdoor heat exchanger 7, move in the rowdirection while flowing back and forth in the direction in which thefins 20 are layered, and then merge at the outdoor outlet header 17 b.In contrast, a flow of the outside air generated by the outdoor fan 8(not illustrated) moves from the right side to the left side on thedrawing, so that a commonly-called counter flow is formed, in which theair and the refrigerant exchange heat between the air inlet side and therefrigerant outlet side and between the air outlet side and therefrigerant inlet side. The indoor heat exchanger 12 also has the sameconfiguration as this configuration, in which the refrigerant inlet andthe air outlet are thermally in contact with each other, while therefrigerant outlet and the air inlet are thermally in contact with eachother. Subsequently, refrigerant control during cooling operation andduring heating operation is described.

Cooling Operation

During cooling operation, in the four-way valve 6 illustrated in FIG. 1, an internal flow path is set in a direction of the solid line.Refrigerant discharged from the compressor 5 enters the outdoor bridgecircuit 10 via the four-way valve 6. The refrigerant having entered theoutdoor bridge circuit 10 passes through the check valve 11 a, andenters the indoor heat exchanger 12 from the inlet header 17 a. At thistime, the check valve 11 b is closed because the pressure on the outletside is increased to a high level. The refrigerant, having transferredheat to the outside air in the indoor heat exchanger 12 and thencondensed and liquified, passes through the outdoor outlet header 17 b,enters the outdoor bridge circuit 10 again, and is then reduced inpressure by the outdoor expansion valve 9 into low-pressure two-phaserefrigerant. The opening degree of the outdoor expansion valve iscontrolled, for example, in such a manner that the temperature of gasrefrigerant discharged from the compressor 5 reaches its target value.

The refrigerant in a low-pressure two-phase state having flowed out ofthe outdoor unit 1 passes through the liquid pipe 4 and enters theindoor unit 2. In the indoor unit 2, the refrigerant enters the indoorbridge circuit 15, passes through the check valve 16 c, and enters theindoor heat exchanger 12 from the indoor inlet header 18 a. At thistime, the indoor expansion valve 14 is closed to prevent the refrigerantfrom flowing through the indoor expansion valve 14.

The refrigerant having entered the indoor heat exchanger 12 is heated bythe room air, then evaporates into low-pressure gas refrigerant, andflows out of the indoor outlet header 18 b. The refrigerant havingflowed out of the indoor heat exchanger 12 enters the indoor bridgecircuit 15 again, passes through the check valve 16 b, and flows out ofthe indoor unit 2.

The refrigerant having flowed out of the indoor unit 2 flows through thegas pipe 3, returns to the outdoor unit 1, and is then suctioned intothe compressor 5 via the four-way valve 6. In this manner, thenon-azeotropic refrigerant filled in the refrigeration cycle device 100circulates in the refrigerant circuit to perform cooling operation.

As explained above, during cooling operation, since the refrigeranthaving condensed in the outdoor heat exchanger 7 is reduced in pressureby the outdoor expansion valve 9, the refrigerant flowing through theliquid pipe 4 is low-pressure two-phase refrigerant. The temperature ofthe low-pressure two-phase refrigerant is relatively low. When theliquid pipe 4 is in contact with the outside air, condensation of watercontained in the outside air can occur. It is thus necessary to insulatethe liquid pipe 4 sufficiently. Meanwhile, the density of thelow-pressure two-phase refrigerant is lower than that of high-pressureliquid refrigerant having condensed in the outdoor heat exchanger 7.Thus, the amount of refrigerant filled in the refrigerant circuit can bereduced.

FIG. 3 is a graph illustrating an example of temperature variations fromwhen refrigerant and air enter the condenser to when the refrigerant andthe air flow out of the condenser. FIG. 4 is a graph illustrating anexample of temperature variations from when refrigerant and air enterthe evaporator to when the refrigerant and the air flow out of theevaporator. In FIGS. 3 and 4 , the vertical axis represents thetemperature, while the horizontal axis represents the relative positionsof refrigerant and air on the path extending from the inlet to theoutlet of the heat exchanger. Since the condenser and evaporatorillustrated in FIGS. 3 and 4 have a structure to form a counter flow,refrigerant flows through the condenser or the evaporator from theleft-side end A toward the right-side end B on the horizontal axis,while air flows through the condenser or the evaporator from theright-side end B toward the left-side end A. The section C on thehorizontal axis shows that the refrigerant is in a two-phase gas-liquidstate.

FIG. 3 illustrates variations in the temperature of air and thetemperature of refrigerant inside the outdoor heat exchanger 7 thatoperates as a condenser during cooling operation in this embodiment. Therefrigerant enters the outdoor heat exchanger 7 in a high-temperaturegas state at a temperature of approximately 70° C. This refrigerantflows through the outdoor heat exchanger 7, is cooled by the air, andthen starts liquefying at a temperature of around 50° C. Since therefrigerant is a non-azeotropic refrigerant mixture, the temperature ofthis refrigerant gradually decreases even in the section C in which therefrigerant is in a two-phase state, and further decreases even afterthe refrigerant has liquefied completely. On the outlet side of theoutdoor heat exchanger 7, the refrigerant is cooled to a temperatureclose to the air inlet temperature at 35° C. to ensure a predetermineddegree of subcooling. Thereafter, the refrigerant flows out of theoutdoor heat exchanger 7. In contrast, a phase change of the air doesnot occur during the process of exchanging heat. Thus, after enteringthe outdoor heat exchanger 7 at a temperature of 35° C., the air isheated with heat from the refrigerant, which simply increases the airtemperature.

In the condenser having the structure to form a counter flow asdescribed above, the air at a sufficiently high temperature on the airoutlet side exchanges heat with high-temperature gas refrigerant on therefrigerant inlet side, while the subcooled liquid refrigerant on therefrigerant outlet side exchanges heat with the outside air on the airinlet side. Even after the refrigerant has changed from the two-phasegas-liquid state to a single-phase liquid state, a sufficienttemperature difference between this refrigerant and the air is stillensured, so that the condenser can exchange heat with high efficiency.

FIG. 4 illustrates temperature variations in the indoor heat exchanger12 that serves as an evaporator during cooling operation in thisembodiment. Refrigerant that enters the indoor heat exchanger 12 is in alow-pressure two-phase state at a temperature of approximately 10° C. atthe refrigerant inlet A. The temperature of the refrigerant graduallyincreases, while this refrigerant exchanges heat with the room air. Thisrefrigerant flows out of the section C showing that the refrigerant isin a two-phase state. Thereafter, the refrigerant further exchanges heatwith the room air, and then flows out of the refrigerant outlet B in alow-pressure gas state with a predetermined degree of superheat.

In contrast, the temperature of air at the air inlet B is the roomtemperature at approximately 27° C. The air is cooled by the refrigerantto a lower temperature of approximately 15° C. at the air outlet A. Thecooling operation is performed by delivering this lower-temperature airto the room.

In the evaporator having the structure to form a counter flow asdescribed above, due to the properties of non-azeotropic refrigerantmixture, the refrigerant and the air exchange heat at the refrigerantinlet where the refrigerant temperature is lowest and at the air outletwhere the air temperature is lowest. This allows the evaporator toefficiently cool the air, and also allows the refrigerant to exchangeheat with the room air on the refrigerant outlet side where the room airis maintained at a high temperature. Thus, the refrigerant can obtain asufficient degree of superheat.

Heating Operation

During heating operation, in the four-way valve 6 illustrated in FIG. 1, an internal flow path is set in a direction of the dotted line.Refrigerant discharged from the compressor 5 flows out of the outdoorunit 1 via the four-way valve 6. The refrigerant having flowed out ofthe outdoor unit 1 enters the indoor unit 2 via the gas pipe 3, andinitially enters the indoor bridge circuit 15. In the indoor bridgecircuit 15, the refrigerant passes through the check valve 16 a, thenflows out of the indoor bridge circuit 15, and enters the indoor heatexchanger 12 from the indoor inlet header 18 a. At this time, the checkvalve 16 b is closed because the pressure on the outlet side isincreased to a high level.

In the indoor heat exchanger 12, refrigerant transfers heat to the roomair to condense and liquify, and then flows out of the indoor heatexchanger 12 from the indoor outlet header 18 b. The refrigerant havingflowed out of the indoor heat exchanger 12 enters the indoor bridgecircuit 15 again, and is reduced in pressure by the indoor expansionvalve 14 to be brought into a low-pressure two-phase state.

The refrigerant having been brought into a low-pressure two-phase stateflows out of the indoor unit 2, and then enters the outdoor unit 1 viathe liquid pipe 4. In the outdoor unit 1, the refrigerant passes throughthe check valve 11 c provided in the outdoor bridge circuit 10, andenters the outdoor heat exchanger 7 from the outdoor inlet header 17 a.

In the outdoor heat exchanger 7, refrigerant is heated by the outsideair to be brought into a low-pressure gas state, and enters the outdoorbridge circuit 10 again via the outdoor outlet header 17 b. At thistime, the outdoor expansion valve 9 is closed, and thus the refrigerantpasses through the check valve 11 b and flows out of the outdoor bridgecircuit 10. Subsequently, the refrigerant is suctioned into thecompressor 5 again via the four-way valve 6.

As described above, in the refrigeration cycle device 100 in the presentEmbodiment 1, refrigerant flowing through the outdoor heat exchanger 7and the indoor heat exchanger 12 forms, along with the air, a counterflow not only during cooling operation, but also during heatingoperation. With this configuration, the heat exchangers ensure asufficient temperature difference between the air and the refrigerantfrom their inlet to outlet, and can thereby exchange heat efficiently,so that the performance of the refrigeration cycle device is improved.This effect is exhibited significantly when the refrigeration cycledevice 100 uses a non-azeotropic refrigerant mixture.

Note that while a bridge circuit is accommodated in each of the outdoorunit 1 and the indoor unit 2 in the present embodiment, even when eitherthe outdoor unit 1 or the indoor unit 2 is provided with the bridgecircuit, the heat exchange efficiency in either one provided with thebridge circuit is still improved. Therefore, the effect of improving theperformance of the refrigeration cycle device can be obtained.

Further, in the refrigeration cycle device in the present embodiment,refrigerant flowing through the liquid pipe 4 is brought into alow-pressure two-phase state not only during cooling operation, but alsoduring heating operation. The liquid pipe 4 is not filled with liquidrefrigerant in any operational state, so that the amount of refrigerantfilled in the refrigerant circuit can be reduced.

Embodiment 2

FIG. 5 is a refrigerant circuit configuration diagram of a refrigerationcycle device 101 according to Embodiment 2 of the present disclosure. Incontrast to the refrigeration cycle device 100 according to Embodiment1, the refrigeration cycle device 101 includes a check valve 11 dinstalled in the flow path of an outdoor bridge circuit 110, in whichthe outdoor expansion valve 9 is located. In the flow path of an indoorbridge circuit 115, in which the indoor expansion valve 14 is located, acheck valve 16 d is installed and also a rectifier 20 is installed onthe upstream side of the indoor expansion valve 14.

In the outdoor bridge circuit 110, the check valve 11 d mechanicallyblocks the flow path provided with the outdoor expansion valve 9 toprevent the refrigerant, entering the outdoor unit 1 from the liquidpipe 4 during heating operation, from flowing toward the outlet side ofthe indoor heat exchanger 12. Due to this configuration, a refrigerantcircuit for heating operation is formed without fully closing theoutdoor expansion valve 9 during heating operation.

The operation of the expansion valve to be fully closed often involvesoperation of the valve body frequently colliding against the valve seat.Thus, particularly on such an operational condition that cooling andheating are alternately performed, this operation promotes the wearingout of the expansion valve. According to the present embodiment, thenumber of times of controlling the opening degree of the outdoorexpansion valve 9 is decreased, so that deterioration of the outdoorexpansion valve 9 over time can be reduced.

Similarly to the outdoor bridge circuit 110, in the indoor bridgecircuit 115, the check valve 16 d mechanically stops refrigerant fromflowing from the liquid pipe 4 toward the outlet side of the indoor heatexchanger 12 during cooling operation. This eliminates the need forfully closing the outdoor expansion valve 14 during cooling operation.This decreases the number of times of controlling the opening degree ofthe indoor expansion valve 14, so that deterioration of the indoorexpansion valve 14 over time can be reduced.

FIG. 6 is a sectional view illustrating the flow path configurationprovided with the indoor expansion valve 14 in the indoor bridge circuit115. A rectifier 20 includes a rectification portion 21 therein. Therectification portion 21 is made of metallic mesh or foam metal. Even ina circumstance where bubbles do not continuously flow to the inlet ofthe expansion valve 14, such as a case where a refrigerant distributionis unstable immediately after the refrigeration cycle device 100 hasstarted heating operation, the rectifier 20 still converts the bubblesto a uniform flow of bubbles in the rectification portion 21. Thisprevents generation of irregular vibration or refrigerant flow sound inthe indoor expansion valve 14, and ensures the comfort of the roomenvironment without being impaired by noise from the refrigeration cycledevice.

As described above, the refrigeration cycle device 101 according toEmbodiment 2 can achieve the same effects as those obtained by therefrigeration cycle device 100 according to Embodiment 1. Further, therefrigeration cycle device 101 includes the check valves 11 d and 16 d,so that the number of times of controlling the opening degree of theoutdoor expansion valve 9 and the indoor expansion valve 14 isdecreased, and thus deterioration of the expansion valves over time canbe reduced. Furthermore, the refrigeration cycle device 101 includes therectifier 20, and therefore can provide comfortable air-conditionedenvironment without generating refrigerant flow sound or irregularvibration in the room.

Embodiment 3

FIG. 7 is a refrigerant circuit configuration diagram of a refrigerationcycle device 102 according to Embodiment 3 of the present disclosure. Incontrast to the refrigeration cycle device 100 according to Embodiment1, the refrigeration cycle device 102 has an indoor bridge circuit 215that is located independently from the indoor unit 2, instead of beingincorporated in the indoor unit 2. Indoor units 2 a, 2 b, and 2 c areconnected in parallel to the indoor bridge circuit 215, and includeopening-closing valves 22 a, 22 b, and 22 c, respectively, on therefrigerant inlet side of indoor heat exchangers 12 a, 12 b, and 12 c.The opening-closing valves 22 a, 22 b, and 22 c can block refrigerantfrom flowing through the indoor heat exchangers 12 a, 12 b, and 12 c.

The refrigeration cycle device 102 is an air-conditioning device formultiple rooms. The indoor units 2 a, 2 b, and 2 c are installed in therespective rooms to control the air temperature in their respectiverooms. At this time, assuming that each of the indoor units 2 a, 2 b,and 2 c is provided with each individual indoor bridge circuit 15 asdescribed in Embodiment 1 or Embodiment 2, the air conditioning capacitycannot be adjusted for each individual room during cooling operation.For this reason, when the air conditioning loads are unbalanced betweenthe rooms, the air conditioning capacity may be excessive orinsufficient depending on the air conditioning load in each of therooms.

The refrigeration cycle device 102 includes the opening-closing valves22 a, 22 b, and 22 c in individual indoor units. Thus, when the airconditioning capacity becomes excessive for a certain room duringcooling operation or heating operation, the correspondingopening-closing valve is closed temporarily to prevent the airconditioning capacity for the certain room from being fully utilized.With this configuration, even when a plurality of indoor units areconnected, it is still possible to independently control the airconditioning capacity for each individual indoor unit, so that therefrigeration cycle device 102 can provide comfortable air-conditionedenvironment.

Since the refrigeration cycle device 102 has a configuration in which aplurality of indoor units are connected to a single unit of indoorbridge circuit 215, the number of components that make up the bridgecircuit, such as a check valve, is reduced, and accordingly themanufacturing costs are reduced.

As described above, the refrigeration cycle device 102 according toEmbodiment 3 can still achieve the same effects as those obtained by therefrigeration cycle device 100 according to Embodiment 1, even when therefrigeration cycle device 102 connects to a plurality of indoor unitsto serve as an air-conditioning device for multiple rooms. That is, theoutdoor heat exchanger 7 and the indoor heat exchangers 12 a, 12 b, and12 c can form a counter flow, and also change the refrigerant flowingthrough the liquid pipe 4 to low-density two-phase refrigerant not onlyduring cooling, but also during heating. Further, the air conditioningcapacity for each individual indoor unit can be adjusted, so that evenwhen the air conditioning loads are unbalanced between the rooms, therefrigeration cycle device 102 can still provide comfortableair-conditioned environment.

The refrigerant circuit is made up of a single unit of indoor bridgecircuit 215 for a plurality of indoor units 2 a, 2 b, and 2 c, so thatthe number of components that make up the refrigerant circuit, such as acheck valve, is reduced and accordingly the manufacturing costs can bereduced.

Embodiment 4

FIG. 8 is a refrigerant circuit configuration diagram of a refrigerationcycle device 103 according to Embodiment 4 of the present disclosure. Incontrast to the refrigeration cycle device 100 according to Embodiment1, the refrigeration cycle device 103 uses a mechanical fixed throttle31 such as a capillary tube as an expansion unit incorporated in anindoor bridge circuit 315. The outdoor expansion valve 9 is notincorporated in the outdoor bridge circuit 10, but is located betweenthe liquid pipe 4 and one end of the outdoor bridge circuit 10.

In the indoor bridge circuit 315, the fixed throttle 31 located inseries to the flow path provided with the check valve 16 d is designedto have such a flow resistance as to reduce the pressure ofhigh-pressure liquid refrigerant, having flowed out of the indoor heatexchanger 12 during heating operation, to a two-phase gas-liquid state.During heating operation, the refrigerant having been brought into atwo-phase gas-liquid state by the fixed throttle 31 enters the outdoorunit 1 via the liquid pipe 4.

The refrigerant having entered the outdoor unit 1 is further reduced inpressure by the outdoor expansion valve 9, and thereafter enters anoutdoor bridge circuit 310. At this time, the opening degree of theoutdoor expansion valve 9 is controlled, for example, in such a mannerthat the temperature of gas discharged from the compressor 5 reaches itstarget value. That is, in the refrigeration cycle device 103 accordingto the present Embodiment 4, first the fixed throttle 31 located in theoutdoor bridge circuit 315 reduces the pressure of refrigerant thatflows through the liquid pipe 4 into a two-phase state, and further theoutdoor expansion valve 9 reduces the pressure of this refrigerant to anappropriate level.

Since the indoor bridge circuit 315 is made up of only the check valves16 a, 16 b, 16 c, and 16 d, and the fixed throttle 31, the indoor bridgecircuit 315 does not need a power source or a signal for controlling theopening degree. Due to this configuration, it is unnecessary to connectelectric wires to the indoor bridge circuit 315, so that theinstallation location is less limited, while the installation work issimplified.

The opening degree of the outdoor expansion valve 9 is controlled notonly during cooling operation, but also during heating operation. Thus,when only the outdoor unit 1 is provided with a controller for theexpansion valve, it is still possible to control the flow rate ofrefrigerant, and costs of the components such as an electric circuit canbe reduced.

As described above, the refrigeration cycle device 103 according toEmbodiment 4 can achieve the same effects as those obtained by therefrigeration cycle device 100 according to Embodiment 1. That is, theoutdoor heat exchanger 7 and the indoor heat exchanger 12 can form acounter flow, and also change the refrigerant flowing through the liquidpipe 4 to low-density two-phase refrigerant not only during cooling, butalso during heating.

The indoor bridge circuit 315 is made up of only mechanical components,so that electric wires are not needed and therefore costs of theinstallation work can be reduced.

The opening degree of the outdoor expansion valve 9 is controlled toadjust the flow rate of refrigerant not only during cooling operation,but also during heating operation. It is thus unnecessary to provide anexpansion valve drive circuit on the indoor side, and accordingly costsof the electric components can be reduced.

The configurations described in the foregoing embodiments are examplesof the present disclosure. Combining these configurations with otherpublicly known techniques is possible, and partial omissions andmodifications of the configurations are possible without departing fromthe spirit of the present disclosure.

REFERENCE SIGNS LIST

1: outdoor unit, 2, 2 a, 2 b, 2 c: indoor unit, 3: gas pipe, 4: liquidpipe, 5: compressor, 6: four-way valve, 7: outdoor heat exchanger, 8:outdoor fan, 9: outdoor expansion valve, 10, 110, 310: outdoor bridgecircuit, 11 a, 11 b, 11 c, 11 d: outdoor check valve, 12, 12 a, 12 b, 12c: indoor heat exchanger, 13, 13 a, 13 b, 13 c: indoor fan, 14: indoorexpansion valve, 15, 115, 215, 315: indoor bridge circuit, 16 a, 16 b,16 c, 16 d: indoor check valve, 17 a: outdoor inlet header, 17 b:outdoor outlet header, 18 a: indoor inlet header, 18 b: indoor outletheader, 20: rectifier, 21: rectification portion, 22 a, 22 b, 22 c:opening-closing valve, 31: fixed throttle, 100, 101, 102, 103:refrigeration cycle device

1. A refrigeration cycle device comprising: an outdoor unit including acompressor, a four-way valve, an outdoor heat exchanger, and an outdoorexpansion valve, the four-way valve being configured to switch betweencooling operation and heating operation; an indoor unit including anindoor heat exchanger and an indoor expansion valve; and a gas pipe anda liquid pipe configured to connect the outdoor unit and the indoor unitto form a refrigerant circuit, the refrigerant circuit being filled withrefrigerant, wherein the refrigeration cycle device comprises at leasteither one of a first bridge circuit accommodated in the outdoor unit,the first bridge circuit having a configuration including a plurality offlow path opening-closing units to allow the refrigerant to flow throughthe outdoor heat exchanger in a same direction both during the coolingoperation and during the heating operation, a flow path opening-closingunit of the plurality of flow path opening-closing units, installed in aflow path connecting the liquid pipe and an outlet side of the outdoorheat exchanger, being the outdoor expansion valve, and a second bridgecircuit having a configuration including a plurality of flow pathopening-closing units to allow the refrigerant to flow through theindoor heat exchanger in a same direction both during the coolingoperation and during the heating operation, a flow path opening-closingunit of the plurality of flow path opening-closing units, installed in aflow path connecting the liquid pipe and an outlet side of the indoorheat exchanger, being the indoor expansion valve, wherein the liquidpipe is configured to allow the refrigerant to flow from the outdoorunit to the indoor unit in the cooling operation and allow therefrigerant to flow from the indoor unit to the outdoor unit in theheating operation.
 2. The refrigeration cycle device of claim 1, whereinthe first bridge circuit includes a first check valve located in seriesto the outdoor expansion valve and configured to stop the refrigerantfrom flowing through the outdoor expansion valve during the heatingoperation.
 3. The refrigeration cycle device of claim 1, wherein thesecond bridge circuit includes a second check valve located in series tothe indoor expansion valve and configured to stop the refrigerant fromflowing through the indoor expansion valve during the cooling operation.4. The refrigeration cycle device of claim 1,wherein the second bridgecircuit includes a rectification unit on an upstream side of the indoorexpansion valve, the rectification unit being configured to allow therefrigerant to flow in a uniform state.
 5. A refrigeration cycle devicecomprising: an outdoor unit including a compressor, a four-way valve, anoutdoor heat exchanger, and an outdoor expansion valve, the four-wayvalve being configured to switch between cooling operation and heatingoperation; a plurality of indoor units each including an indoor heatexchanger and a solenoid valve; a first bridge circuit accommodated inthe outdoor unit, the first bridge circuit having a configurationincluding a plurality of flow path opening-closing units toallowrefrigerant to flow through the outdoor heat exchanger in a samedirection both during the cooling operation and during the heatingoperation, a flow path opening-closing unit of the plurality of flowpath opening-closing units, installed in a flow path connecting a liquidpipe and an outlet side of the outdoor heat exchanger, being the outdoorexpansion valve; a second bridge circuit to which each of the pluralityof indoor units is connected in parallel, the second bridge circuithaving a configuration including a plurality of flow pathopening-closing units to allow the refrigerant to flow through each ofthe plurality of indoor units in a same direction both during thecooling operation and during the heating operation, the second bridgecircuit including an indoor expansion valve in a flow path connectingthe liquid pipe and an outlet side of each of the plurality of indoorunits; and a gas pipe and a liquid pipe configured to connect theoutdoor unit and the second bridge circuit to form a refrigerantcircuit, the refrigerant circuit being filled with refrigerant. 6.(canceled)
 7. The refrigeration cycle device of claim 1, wherein therefrigerant is a non-azeotropic refrigerant mixture made up of two ormore types of refrigerants with different boiling points.